1. Technical Field of the Invention
The present invention relates to an automatic locking apparatus which automatically locks doors of a vehicle.
2. Related Art
Japanese Unexamined Patent Application Publication No. 2005-213987 discloses a door locking apparatus for a vehicle, which is one example of a conventional technique for automatically locking doors of a vehicle.
The above door locking apparatus includes a portable unit, which a passenger of the vehicle carries, and an in-vehicle unit, which is provided in the vehicle. When a door is dosed, a transmitter of the in-vehicle unit transmits a request signal to the portable unit. Then, when a receiver of the in-vehicle unit cannot receive checking data from the portable unit within a predetermined period of time, the in-vehicle unit locks the door. Accordingly, in the case where outputs of the transmitter and the receiver are adjusted, and the communication area is set inside the vehicle (in the interior of the vehicle) and at the periphery of the vehicle, the door can be quickly locked immediately after the passenger carrying the portable unit gets out of the vehicle.
Meanwhile, in the communication area at the periphery of the vehicle (detection area of the portable unit), a case can be assumed that a state in which checking data transmitted from the portable unit can be received changes to a state in which the checking data cannot be received. In this case, the door may be automatically locked after confirming that the passenger carrying the portable unit has got out of and gone away from the vehicle.
However, in the case where a plurality of passengers open the doors corresponding to a plurality of seats such as the driver's seat and the passenger seat and get out of the vehicle, when the passenger carrying the portable unit closes the door before the other passengers close the doors, and leaves the communication area, the doors may not be automatically locked. Hence, the passenger carrying the portable unit has to wait near the vehicle until all the doors are closed.